Floor and method of laying it



Sept. 25, 1962 A. ELMENDORF 3,055,065

FLooRfAND METHOD oF 1.1mm: 1T

Fil'ed Oct. 8, 1958 I 2 Sheets-Sheet 2 IN V EN TOR.

United States Eatent 3,055,65 FLOOR AND METHOD F LAYING IT Armin Elmendorf, 860 Charleston Road, Palo Alto, Calif. Filed Oct. 8, 1958, Ser. No. 766054I 2 Claims. (Ci. 20-39) My invention relates to an improvement in wood flooring and in methods of laying the same and is a continuation-in-part of my copending application Serial No. 764,- 932, `filed October 2, 1958.

One purpose is to provide a exible iiooring made of hardwood veneer, which may be bonded to all types of sub-oors suitable for flexible floor coverings such as linoleum.

Another purpose is to provide such a flexible hardwood veneer ooring which may be laid over concrete subiiooring.

Another purpose is to provide such a floor in which the individual panels may be laid edge to edge, with no intervening gap between adjacent panels or between the marginal panels and the circumferential walls.

Another purpose is to provide a flexible wood flooring which may be applied to a supporting surface by momentary pressure on the job.

Other purposes will appear from time to time in the course of the specification and claims.

In the installation of a flexible ooring made of hardwood veneer it must be possible to bond the flooring to all types of sub-floors over which other flexible floor coverings are used. Where wood iloors are used over concrete two adverse conditions are frequently encountered. The rst of these is the presence of moisture in or on the concrete. This is so hazardous to the use of some floor coverings, as, for example, linoleum, that manufacturers of that product often advise against the use of the same when the concrete is on grade. Veneer, unless specially treated expands so much in the presence of moisture that the results with it are even more unsatisfactory than those obtained with linoleum. A second condition which causes difficulty is an uneven concrete surface due to unsatisfactory nish trowelling.

The presence of moisture on concrete may be partially combated by the employment of an asphalt-saturated membrane between the flooring and the concrete. But such membranes generally contain cellulosic fibers, and these are susceptible to action of the caustic in damp concrete. I have found that by using a thick asphaltsaturated felt faced on one side with a layer of mineral granules, and the membrane is bonded to the concrete with an alkali-resistant adhesive, with the granules down and in contact with the adhesive, the cellulosic `libres of the membrane, as well as wood iiooring above it, are protected from the alkali of the concrete. The concrete should, of course, be dry but certainty regarding dryness is not readily achieved.

Another serious problem encountered by all wood floors, irrespective of the type of sub-ooring is the expansion of the wood due to increase in hygroscopic moisture resulting from exposure to prolonged periods of high atmospheric humidity. This problem is chronic and when not taken care of adequately results in buckling of the floor. A buckled wood oor is so common that the use of a pattern wood floor in places where is cannot be nailed is considerably restricted. When laying a wood iioor, for example, in the form of squares, the component slats of which the squares are composed may be spaced apart to provide room for expansion, or gaps of adequate width may be provided around the perimeter of the square, or wide spaces may be provided around the perimeter of the room under the base board into which the wood can expand. All of these procedures require the use of a solee called mastic for bonding, that is, an adhesive which yields slowly under stress. Normal adhesives of the rigid or elastic type are not satisfactory. Moreover, wood block oors must be made thick in order to delay changes in moisture, much thicker than wear requires. Except in museums ywhere the traflic is high, the wear of a hardwood oor is rarely as much as 1ALG-inch even after a generation of use, yet the floor must be made 3Mt-inch thick in order to reduce moisture changes resulting from high atmospheric humidity. One of the main purposes of the present invention is to greatly reduce this economic waste.

It should be pointed out that the provision of spaces around the blocks of wood squares or along the edges of plank flooring is universally disapproved of by the public who maintain that the cracks catch dirt. One of the purposes of the present invention 4is to provide a wood oor that will not buckle in high humidity weather and simultaneously is free of visible cracks I illustrate my invention more or less diagrammatically in the accompanying drawings wherein:

FIGURE l shows a plan view of the wood panels of my invention when produced in the form of squares and bonded to a sub-floor;

FIGURE 2 is a similar plan view of another form of my flooring made in the form of planking;

FIGURE 3 is a diagrammatic illustration of the method of laying the panels of FIGURES l and 2;

FIGURE 4 illustrates one form of my flexible flooring consisting of two plies bonded together in a special manner; and

FIGURE 5 illustrates another form of the flexible ilooring consisting of a single layer of wood treated against expansion ruptured along the grain and distended to provide room for residual expansion.

Like parts are indicated by like symbols throughout the speciiication and drawings.

As shown in FIGURES l and 3, the ilooring units 1, 2 are in the form of squares conventionally laid in checkerboard fashion. While I do not wish to be limited to a specific size of unit, I nd that 9 x 9-inch squares form practical units.

Whereas I have shown only squares laid in checkerboard fashion, or wide planks laid side by side, it will be understood that I may employ units of other shapes, laid at an angle, for example rectangles laid in a herringbone pattern.

In the manufacture of my exible flooring I start with freshly cut green veneer which is at least j/lo-inch thick for single-ply flooring and at least 1/ls-inch thick in the case of the Z-ply construction. The rst Step is to process the wood so that its subsequent expansion in use from its equilibrium condition is greatly reduced. This may be done in several ways as by drying the wood under constraint or by impregnating the wood with an appropriate resin and then drying it. I prefer drying under constraint because it is faster and less costly. My experience has shown that, irrespective of the means used, the capacity to expand must be reduced to less than half the capacity of the untreated or unprocessed wood in order toy make the subsequent provision for accommodating the residual expansion eective. By drying under constraint, using an appropriate Ventilating caul, the width of the veneer at equilibrium moisture, that is, at its average moisture content in use as ilooring is nearer to its green width than it is to the width of the same veneer dried to equilibriums without constraint. The dry veneer, irrespective of the method used for reducing expansion, has an equilibrum moisture in use in most areas of the United States of less than 10%. A-t that moisture content the width of the wood processed against expansion v93% of their green width.

should preferably be at least 97% of its green width although this depends to some extent on the species of wood used. As many hardwood veneers suitable for flooring shrink as much las 7% or more when drying freely to equilibrium, their ldry width may be less than By drying under constraint, I can thereby reduce theV capacity of the wood to expand in use to less than half the capacity of the same Wood dried normally without constraint.

Drying under constraint has another advantage over impregnation with a synthetic resin, as with one of the urea vresins or an appropriate sugar, in that the resultant sheet is much atter than a dry impregnated sheet. Flatness is important in a Hoor panel that is to be bonded with an adhesive to a sub-Hoor using momentary pressure.

A thin hardwood floor which canrbe bonded on the job with an adhesive using momentary pressure I have found must not only be dat and llexible and the wood of which it is composed must not only be processed against expansion, but `the residual capacity to expand must be accommodated. This I have found can be done by expanding the wood as in flexing, to break it down into many narrow elements each separated by minute gaps or ssures following the grain of the wood that are so line lthat their presence is not readily detected, yet

sufficiently great to provide room into which the element can expand and so to relieve the wood of substantially all expansion stresses. The space so provided must not be less than the residual expansion in the element which had previously been dried under constraint. I have found that such spaces can be provided by iiexing the veneer that had been dried under constraint until it has been broken down into narrow elements without appreciable structural connection. By this means gaps between the elements can be produced whose width ranges from 2% to 6% of the width of the element. I have found by experience that this is sutiieient to accommodate the residual expansion.

The distance between gaps I nd may average anywhere from 1/16 of `an inch to 1A of an inch. However, this average is given as an example and not as a matter of limitation. In practice, the width of the minute gaps resulting from flexing the wood is greater .than 2% but less than 6% of the average width of the space between gaps. The wood between the gaps has a width greater than its equilibrium width when dried without constraint. Actually, the width of the wood between the gaps is nearer to the Width it had in the green condition than it is to the equilibrium width when the wood is dried without constraint.

By equilibrium width, I mean the width of the wood or veneer when it reaches constant weight at average room conditions. Every piece of wood has an equilibrium width which is determined by the humidity of the air that surrounds it. Although the humidity changes, there is always a lag in change of moisture content in the wood, because 'the moisture content is not quickly changed. In most parts of the United States the equilibrium moisture content of wood ilooring under room conditions ranges from 8% to 10%. The equilibrium width is, therefore, generally `the width the wood has when its moisture content is about 8% to 10%. In some areas, for example, along the Gulf of Mexico, the equilibrium moisture content of wood flooring may be higher than 10%. In other areas, for example, the desert areas of the Southwest, the equilibrium moisture content may be less than 8%. tI should be noted in Vthis connection that veneers of the thickness required for flooring are still much thinner than 3t-inch, the thickness of conventional hardwood flooring, hence the veneers are more susceptible to moisture change than conventional flooring. Hence the importance of processing the wood to bring the resultant expansion under control.

In FIGURE 4, I illustrate a two-ply panel which is formed of two layers of veneer. both layers being treated' as described above and then flexed and expanded. Both plies are ruptured into narrow elements separated by fine fissures or gaps following the grain. The flexible veneer sheets may have a thickness of the order of 1/10 of an inch to 2/10 of an inch.

The veneer must not be thinner than l/l of an inch in order to provide adequate resistance to wear. Because of the thinness of the layer, I prefer to employ hardwoods, although the invention is not limited to any specic wood or woods.

I have found by experience that when two plies are bonded together as shown in FIGURE 4, the average angle 'between the ssures of one ply and those of the second ply must lie between 3 degrees and 20 degrees in order to prevent tearing in handling and at the same time to get a panel that does not warp.

If a single ply is used, such as shown in FIGURE 5, that ply will be of the order of twice the thickness of the individual plies 7 and S shown in FIGURE 4. Whether I employ one or two plies, it is essential that the rveneer be ruptured along the grain and expanded, the narrow elements formed thereby being composed of structurally separated units, Athe wood being provided with gaps between the elements following the wood grain at narrow intervals, the average width of the gaps being greater than 2% but less than 6% of the average width of the space between the gaps, the wood between the gaps having a width greater than its equilibrium width when dried freely. When laid in the form of squares, as in FIGURES l and 3, the wood grain of one square is at right angles to the grain of the adjacent square.

In applying the flexible wood panels to a support, -for example, a concrete sub-floor, as illustrated at 10 in FIG- URE 3, the floor is generally surrounded by a wall which may include studding 11 and wallboards 12. In the structure as shown in FIGURE 3, exible expanded wood squares 1 and 2 are laid with the grain and iissures of one square at right angles to those of the adjacent squares. These are laid snugly edge to edge, with no space between the squares. It will be understood, of course, that the parallel planks of FIGURE 2 may be employed, or other forms of the flooring, as above mentioned.

The flooring bonded to the sub-door must remain bonded under the most severe conditions to which it may be exposed in service. Experience has shown that a1- though the ooring is prevailingly installed indoors it may, nevertheless, be exposed to wetting, as from rain coming through an open window or door, or from carelessness in mopping the floor. The ooring must, therefore, not separate from the sub-flooring or underlayment in high humidity weather nor when it is accidentally wetted.

A water-resistant dry bond adhesive of the synthetic rubber type may be employed for bonding the ooring yto the sub-door. Bonding is achieved with such an adhesive by using only momentary pressure, as by means of a heavy roller, or by means of blows from a rubber mallet. A suitable adhesive is diagrammatically illustrated at 13 in FGURE 3. The processed, ruptured and expanded wood panels are suciently flexible and thin enough to conform to the slight irregularities of an underlying concrete sub-floor. They are thick enough to provide adequate wear resistance and, when exposed to wetting, the residual expansion generally does not exceed the space provided in the minute gaps between the narrow elements.

I have found from experience, that the exible wood veneer flooring made as described meets all of the requirements. It may be briefly described as follows:

VThe veneer layers or plies are dried under constraint so that their equilibrium width is nearer their green width than the width they would have if allowed to dry to equilibrium without constraint. The veneer is flexed and expanded and thereby divided into narrow elements with a gap between the elements ranging in width from 2% to 6% the Width of the element. The flooring panels may be bonded to a sub-floor, edge to edge, without an expansion space between the panels, the minute and substantially invisible gaps within the wood, provided by the flexing and expansion, being sucient. The residual expansion potential left in the wood after drying under constraint takes place in these minute and practically invisible gaps. Thus the over-all expansion of the flooring, even when subjected to extreme moisture conditions, has been practically eliminated. There is no cumulative expansion of the flooring as a whole. The residual expansion and subsequent contraction take place in the narrow elements into which the wood has been divided. Since the gaps follow the grain of the wood, the residual expansion takes place at right angles to the grain and is completely accommodated.

For bonding the ooring to the sub-llooring, I prefer an elastic adhesive, as for example, an adhesive made of synthetic rubber. By means of such an adhesive the `slight movement of the narrow wood elements due to residual expansion is taken up in the adhesive and no appreciable shear stresses are set up in the surface of the `sub-flooring. Mastics as used conventionally in laying wood blocks on concrete must not be used.

The use and operation of the invention are as follows:

I provide a thin but wear-resistant ileXible wood iloor covering which may be quickly and economically applied, even to somewhat irregular floor surfaces by means of an adhesive using momentary pressure, which will not buckle in high humidity weather, which withstands wetting and provides room for residual expansion in iine substantially invisible fissures between narrow elements into which the Wood has been divided. Since the residual expansion caused by wetting or increase in hygroscopic moisture is taken up in the body of the panel, I can lay the panels in edge contact, and there is no necessity for leaving spaces between panels or along the walls. I avoid the disadvantage of having cracks in which dirt can collect. I prefer to bond my exible hardwood veneer ooring directly to a ysub-licor with an elastic adhesive. While, by my method, the exible wood panels may be laid `directly on concrete, it will be understood that they may be laid on any sub-floor or underlayment suitable vfor linoleum or other eXible oor coverings. It will also be noted that with veneer 1As-inch thick I use only one-sixth as much wood as in conventional hardwood strip iiooring.

It will be realized that whereas I have described and shown a practical and eicient flooring, and a practical and operative method of laying it, nevertheless, many changes may be made in size, shape and disposition of parts, and in method steps, without departing from the spirit of my invention. I therefore wish my description and drawings to be taken as, in a broad sense, illustrative or diagrammatic, rather than as limiting me to my disclosure herein, except so far as I speccally limit myself by 'the appended claims.

I claim:

1. A veneer flooring which when bonded to a subflooring with an adhesive using momentary pressure and when subsequently exposed to high atmospheric humidities will not buckle, which includes two plies of Veneer divided in-to narrow elements separated by minute iissures that are not readily detected and that follow the grain of the wood into which the wood can expand, the average width of the issures being from 2% to 6% of the average width of the elements and being at least as great as the average expansion of the wood between the iissures, the wood between the issures being nearer to its green Width than to its width when dried freely to equilibrium, the average angle between the iissures of one ply and those of the companion ply being greater than 3 degrees and less than 20l degrees.

2. A pliable wood board composed of two similar wood veneer plies, the veneer being in a ruptured state and being divided into narrow elements without appreciable structural connection, the elements being separated by fissures whose width is from two percent to six percent of the width of the element, the veneer having been dried under constraint so that the capacity of the elements to expand is less than half the capacity of the same wood dried naturally, the average angle of the fissures of one ply with respect to the fissures of the second ply ranging from 3 degrees to 20 degrees.

References Cited in the tile of this patent UNITED STATES PATENTS 1,778,250 Elmendorf Oct. 14, 1930 2,091,476 Elmendorf Aug. 31, 1937 2,268,477 Elmendorf Dec. 30, 1941 2,516,329 Maxey July 25, 1950 2,593,863 Elmendorf Apr. 22, 1952 2,835,936 Elmendorf May 27, 1958 FOREIGN PATENTS 342,695 Great Britain Feb. 2l, 1931 

